Prostaglandin E-2 mediates chorion formation of the Asian tiger mosquito, Aedes albopictus, at late oogenesis

Chorion-i.e., the eggshell-is formed during the late stage of oogenesis by follicular epithelium in the ovary. Although the endocrine signal(s) driving choriogenesis remain unclear in mosquitoes, this process in other insects has been suspected to involve the mediation of prostaglandins (PGs). This study tested the role of PG in the choriogenesis of the Asian tiger mosquito, Aedes albopictus, and its influence on controlling the expressions of genes associated with chorion formation by a transcriptome analysis. An immunofluorescence assay showed that PGE(2) is localised in follicular epithelium. With the treatment of aspirin, an inhibitor of PG biosynthesis, at mid oogenesis, the PGE(2) signal disappeared in the follicular epithelium led to significantly inhibited chorion formation along with a malformed eggshell. Ovary transcriptomes were assessed by RNASeq at the mid and late ovarian developmental stages. Differentially expressed genes (DEGs) exhibiting more than twofold changes in expression levels included 297 genes at mid stage and 500 genes at late stage. These DEGs at these two developmental stages commonly included genes associated with egg and chorion proteins of Ae. albopictus. Most chorion-associated genes were clustered in the 168 Mb region on a chromosome and exhibited significantly induced expressions at both ovarian developmental stages. The inhibition of PG biosynthesis significantly suppressed the expression of the chorion-associated genes while the addition of PGE(2) rescued the gene expressions and led to recovery of choriogenesis. These results suggest that PGE(2) mediates the choriogenesis of Ae. albopictus.

Automated summary

In the Asian tiger mosquito, Aedes albopictus, PGE(2) is localized in the follicular epithelium during early ovarian development. Inhibition of PG biosynthesis during mid-ovarian development leads to the disappearance of PGE(2) signal in the follicular epithelium, resulting in inhibited and malformed chorion formation. Transcriptome analysis revealed significant changes in the expression of genes associated with egg and chorion proteins during mid- and late-ovarian development stages. Inhibition of PG biosynthesis suppressed the expression of chorion-associated genes, while the addition of PGE(2) rescued the gene expressions and promoted choriogenesis.